Semiconductor element, method for manufacturing semiconductor element, semiconductor device, and method for manufacturing semiconductor device

Abstract

A method for manufacturing a semiconductor element includes preparing a semiconductor wafer that includes a substrate including a Ga2O3-based semiconductor and an epitaxial layer including a Ga2O3-based semiconductor and located on the substrate, fixing the epitaxial layer side of the semiconductor wafer to a support substrate, thinning the substrate of the semiconductor wafer fixed to the support substrate, after the thinning of the substrate, forming an electrode on a lower surface of the substrate, bonding or forming a support metal layer on a lower surface of the electrode of the semiconductor wafer, and dicing the semiconductor wafer into individual pieces, thereby obtaining plural semiconductor elements each including the support metal layer. Thermal conductivity of the support metal layer is higher than thermal conductivity of the substrate.

1 . A method for manufacturing a semiconductor element, comprising:
 preparing a semiconductor wafer that comprises a substrate comprising a Ga 2 O 3 -based semiconductor and an epitaxial layer comprising a Ga 2 O 3 -based semiconductor and located on the substrate;   fixing the epitaxial layer side of the semiconductor wafer to a support substrate;   thinning the substrate of the semiconductor wafer fixed to the support substrate;   after the thinning of the substrate, forming an electrode on a lower surface of the substrate;   bonding or forming a support metal layer on a lower surface of the electrode of the semiconductor wafer; and   dicing the semiconductor wafer into individual pieces, thereby obtaining a plurality of semiconductor elements each comprising the support metal layer,   wherein thermal conductivity of the support metal layer is higher than thermal conductivity of the substrate.   
     
     
         2 . The method for manufacturing a semiconductor element according to  claim 1 , wherein in the bonding or forming the support metal layer, a metal plate as the support metal layer is bonded to the electrode by a conductive adhesive, or a plating film as the support metal layer is formed on the electrode by a plating process. 
     
     
         3 . The method for manufacturing a semiconductor element according to  claim 1 , wherein the support metal layer comprises a metal plate comprising a plurality of through-holes penetrating the support metal layer in a thickness direction, or depressions, that are provided along a dicing line, and wherein in the dicing the semiconductor wafer into individual pieces, the support metal layer is cut along the dicing line. 
     
     
         4 . A method for manufacturing a semiconductor element, comprising:
 preparing a semiconductor wafer that comprises a substrate comprising a Ga 2 O 3 -based semiconductor and an epitaxial layer comprising a Ga 2 O 3 -based semiconductor and located on the substrate;   fixing the epitaxial layer side of the semiconductor wafer to a support substrate;   forming a recessed portion on a lower surface of the substrate of the semiconductor wafer fixed to the support substrate;   forming an electrode on the lower surface of the substrate including an inner surface of the recessed portion;   forming a conductor layer on a lower surface of the electrode so as to fill the recessed portion; and   dicing the semiconductor wafer into individual pieces, thereby obtaining a plurality of semiconductor elements,   wherein thermal conductivity of the conductor layer is higher than thermal conductivity of the substrate.   
     
     
         5 . A method for manufacturing a semiconductor device, comprising:
 each step included in the method for manufacturing a semiconductor element according to  claim 1 ; and   fixing the support metal layer side of the semiconductor element to a lead frame or a wiring board, and electrically connecting the support metal layer to the lead frame or wiring on the wiring board,   wherein a thermal expansion coefficient of the support metal layer is between a thermal expansion coefficient of the substrate and a thermal expansion coefficient of the lead frame or a base material of the wiring board.   
     
     
         6 . A method for manufacturing a semiconductor device, comprising:
 each step included in the method for manufacturing a semiconductor element according to  claim 4 ; and   fixing the conductor layer side of the semiconductor element to a lead frame or a wiring board, and electrically connecting the conductor layer to the lead frame or wiring on the wiring board.   
     
     
         7 . A method for manufacturing a semiconductor device, comprising:
 preparing a semiconductor wafer that comprises a substrate comprising a Ga 2 O 3 -based semiconductor and an epitaxial layer comprising a Ga 2 O 3 -based semiconductor and located on the substrate;   fixing the epitaxial layer side of the semiconductor wafer to a support substrate;   forming a recessed portion on a lower surface of the substrate of the semiconductor wafer fixed to the support substrate;   forming an electrode on the lower surface of the substrate including an inner surface of the recessed portion;   dicing the semiconductor wafer into individual pieces, thereby obtaining a plurality of semiconductor elements; and   fixing the semiconductor element to a lead frame comprising a raised portion corresponding to the recessed portion of the substrate so that the raised portion is inserted into the recessed portion, and electrically connecting the electrode to the lead frame.   
     
     
         8 . A semiconductor element, comprising:
 a substrate comprising a Ga 2 O 3 -based semiconductor and having a thickness of not more than 250 µm;   an epitaxial layer comprising a Ga 2 O 3 -based semiconductor and located on the substrate;   a first electrode on an upper surface of the epitaxial layer;   a second electrode on a lower surface of the substrate; and   a support metal layer that is located on a lower surface of the second electrode and has a thermal conductivity higher than a thermal conductivity of the substrate.   
     
     
         9 . The semiconductor element according to  claim 8 , wherein the support metal layer comprises a metal plate bonded to the electrode by a conductive adhesive, or a plating film formed on the electrode. 
     
     
         10 . A semiconductor element, comprising:
 a substrate comprising a Ga 2 O 3 -based semiconductor and comprising a recessed portion on a lower surface thereof;   an epitaxial layer comprising a Ga 2 O 3 -based semiconductor and located on the substrate;   a first electrode on an upper surface of the epitaxial layer;   a second electrode on a lower surface of the substrate; and   a conductor layer that is provided on a lower surface of the second electrode so as to fill the recessed portion and has a thermal conductivity higher than a thermal conductivity of the substrate.   
     
     
         11 . A semiconductor device, comprising:
 the semiconductor element according to  claim 8 ; and   a lead frame or a wiring board on which the semiconductor element is mounted,   wherein the support metal layer side of the semiconductor element is fixed to the lead frame or the wiring board, and the support metal layer is electrically connected to the lead frame or wiring on the wiring board.   
     
     
         12 . A semiconductor device, comprising:
 the semiconductor element according to  claim 10 ; and   a lead frame or a wiring board on which the semiconductor element is mounted,   wherein the conductor layer side of the semiconductor element is fixed to the lead frame or the wiring board, and the conductor layer is electrically connected to the lead frame or wiring on the wiring board.   
     
     
         13 . A semiconductor device, comprising:
 a semiconductor element that comprises a substrate comprising a Ga 2 O 3 -based semiconductor and comprising a recessed portion on a lower surface thereof, an epitaxial layer comprising a Ga 2 O 3 -based semiconductor and located on the substrate, a first electrode on an upper surface of the epitaxial layer, and a second electrode on a lower surface of the substrate; and   a lead frame which comprises a raised portion corresponding to the recessed portion of the substrate and on which the semiconductor element is mounted,   wherein the semiconductor element is fixed to the lead frame so that the raised portion is inserted into the recessed portion, and the second electrode is electrically connected to the lead frame.